Potterton Lynx Boiler problem.. slightly strange.

[Robinm]

I'm very new to the forum and would appreciate some help with this! I have a Potterton Lynx electronic (I'm not sure if that's the 1 or the 2 ?), Yes I know it's old but it does seem rather well built compared to lots of modern stuff and I intent to keep it for a while yet..

The problem is this: When I turn on my bath tap, everything works correctly, I get the DHW Demand light, brief Ignition, low flame and high flame lights.. all normal, however the temperature lights rarely get above the first orange light, also if the flow alters at all (such as with the shower) it's shuts off the heat all together and all the heat lights go out. It has done this a couple of times with the tap on full as well. The central heating appears to work normally but that rarely gets very high on the temp lights either (sometimes two orange lights). Any idea's? Your experiences with this boiler would be appreciated, Great forum! Thanks.

 

[weareleeds]

Make sure flow rate is set to makers spec (probably around 9l/min) which is around 6.5 secs to fill a 1 litre jug

 

[baxpoti]

Start with replacing the dhw sensor

Part No. 430011

It's a wet pocket!

 

[Agile]

The first lynx has a blue PCB with two plug in cards.

The Lynx II has a single coffee coloured PCB.

Both boilers are surprisingly reliable but are getting to the stage when its time to replace.

The Lynx II has a common fault where it works on CH but after going off when temp is reached it never comes back on by itself. It seems to be a PCB fault but I have never needed to find out exactly what.

Tony

 

[pannierstan]

Sounds like you have a Lynx 1 with all the lovely lights on.

My suggestion would be the modulation board.

As Agile said there a 3. A big one which the other 2 plug in to

If it has ignition problems then its the ign sequence board and if as you say its not modulating regardless of temperature then I dont think it is even getting to full flame hence the problem you have.

I have had this problem several times on the lynx. Modulation board sorted it, but you must make sure everything else is right first!

Stan

 

[Agile]

Sometimes it can be something as simple as dirty pin connections on the plug in cards.

It would be worth gently levering them out and then pushing them fully back in just in case.

Tony

 

[Robinm]

A big thank you to you guys for replying, it's much appreciated.. It's defiantely a Lynx 1 with the blue boards.. I have a follow up: The heating is on at the mo and the temperature lights definately climb upwards on CH but not on DHW, I took the cover off last night and traced the DHW temp sensor, it's quite corroded looking compared to the CH temp sensor, I shorted the purple leads together on the DHW sensor and all the lights come on.. has to be a faulty DHW temp sensor? Just how hard are these things to swap out?, I bet it'd be well corroded in there after 10 years, any suggestions of the best way to do this gratefully recieved! (what's best to persuade it out, local heat? penetrating oil 24 hrs?) I should add I'm a qualified electro-mechanical engineer (but nothing 'Gas' of course) and have a garage full of proper tools and a reputation for not breaking things.. The job certainly isn't beyond me by any stretch but I would benefit from you guys giving me your experiences before I start.. Thanks.

 

[Agile]

Before trying to change it measure the resistances of the two sensors with the boiler cold. From memory I think it should be about 10k to 13k.

Just because something looks bad does not mean its faulty. Often its the shiny new bits which have failed!

Just sometimes the sensors go o/c as they get hot.

It could be something else! what happens when you reduce the water flow to just 5 li/min?

Tony

 

[ChrisR]

Erm

if the flow alters at all (such as with the shower) it's shuts off the heat all together and all the heat lights go out.

Is the water flow switch operating properly?

Is this the one with the standardish diverter on the right?
If so check the pin comes out on HW flow to operate the microswitches smartly.